Lint docs: Sort versions, so that stable comes first (#15149)

I expect that most people use stable Clippy. So having `master` be the
first documentation link in the list is weird. Now the versions are
sorted stable->beta->master.

changelog: none
diff --git a/triagebot.toml b/triagebot.toml
index 16557a4..4f37075 100644
--- a/triagebot.toml
+++ b/triagebot.toml
@@ -17,6 +17,9 @@
 
 [issue-links]
 
+[mentions."clippy_lints/src/doc"]
+cc = ["@notriddle"]
+
 # Prevents mentions in commits to avoid users being spammed
 [no-mentions]